Experimental schistosomiasis haematobia investigations have contributed much to a greater understanding of the basic biology of the causative agent responsible for bladder cancer and a severe debilitating disease of man. Studies in this laboratory have also revealed areas in which additional research is warranted. In the coming year work will continue on biologic and pathologic characterization of Schistosoma haematobium with attempts to evaluate potentials for homologous and heterologous immunity. For homologous immunity studies S. haematobium-infected hosts will be challenged with single or multiple exposures to S. haematobium. S. rodhaint-(benign nonhuman schistosome) immunized hamsters and primates will be studied for heterologous immunity or protection after challenge infection with S. haematobium. Investigations will continue to evaluate the possible development of a pedigreed strain of S. haematobium. This is dependent upon passage of the parasite from man through nonhuman primates, circumventing the attenuation of schistosome virility resulting from passage through nonoptimal rodent hosts.